This invention relates to optical coupling.
In various opto-electronic and electro-optical assemblies it is necessary to align elements of the assembly so that light output from one element is input to another element. If the light emitting element emits a diverging beam then in order to couple a substantial portion into the light receiving element it is necessary to position the light receiving facet of the receiving element close to the light emitting facet of the emitting element. In some instances this close positioning cannot be achieved: for example if the light emitting element is on a support that is subject to movement such as thermal expansion or vibration and the light receiving element is such that it can not be flexibly mounted then it becomes difficult to mount the light receiving element sufficiently close to the light emitting element without impariing the performance of the light receiving element. If a common support is used a flexible connection is required between the receiver and the package wall which would restrict the bandwidth due to the effects of parastic capacitances and/or inductances inherent in a flexible connection. On the other hand mounting the receiving element off the transmitting element support increases the distance between the elements and also introduces alignment problems caused by the relative movement of the elements.